Oldest
Antarctic ice core reveals climate history
From British Antarctic Survey
09
June 2004
Secrets
of the Earth's past climate locked in a three-kilometre long Antarctic ice
core are
revealed this week in the journal Nature. The core from Dome C,
high on East Antarctica's plateau, contains snowfall from the last 740,000
years and is by far the oldest continuous climate record obtained from ice cores
so far.
The
ice has been collected in an eight year project by scientists and engineers from
10 European countries. Analysis of
ice cores shows how temperature changed in the past, but also how the
concentrations of gases and particles in the atmosphere varied.
The
first results confirm that over the last 740,000 years the Earth experienced
eight ice ages, when Earth's climate was much colder than today, and eight
warmer periods (interglacials). In
the last 400,000 years the warm periods have had a temperature similar to that
of today. Before that time they
were less warm, but lasted longer.
By
comparing the pattern of this past climate with global environmental conditions
today the scientists conclude that, without human influence, we could expect the
present warm period to last at least another 15 000 years.
The
next step in the research is to extract air from tiny bubbles in the ice, and to
find out how the atmosphere's composition has varied.
Preliminary analyses show that the present carbon dioxide concentration
is the highest level seen in the last 440,000 years.
By understanding what drove past changes in climate, the scientists
expect to improve predictions about future climate.
The
Dome C drilling is part of the ‘European Project for Ice Coring in
Antarctica' (EPICA). The team at Dome C endured summer temperatures as low as
minus 40°C at the remote drilling site over a thousand kilometres from the
nearest research station. The consortium will continue to drill at the site from
December 2004, and hopes to reach the rocks at the base of the ice sheet.
There are just 100 metres still to drill, and if all goes well, the team
will reach ice over 900,000 years old at the base.
Dr
Eric Wolff, from British Antarctic Survey says:
"It's
very exciting to see ice that fell as snow three-quarters of a million years
ago. These results tell us that we
won't have an ice age any time soon. However, we may have a heat wave if we
are unable to control CO2 emissions and other greenhouse gases
entering the atmosphere. Our next
step is to investigate CO2 in the ice cores and by understanding what
has driven the natural changes seen in the ice record, we will create better
models to predict how climate might change in the future."
‘Eight
glacial cycles from an Antarctic ice core' is published in the journal
Nature on 10 June 2004.
EPICA
(European Ice Core Project in Antarctica) is a consortium of 10 European
countries (Belgium, Denmark, France, Germany, Italy, Netherlands, Norway,
Sweden, Switzerland, UK). EPICA is
coordinated by the European Science Foundation (ESF), and funded by the
participating countries and by the European Union.
The
EPICA research team is using the unique climate record from ice cores to
investigate the relationship between the chemistry of the atmosphere and climate
changes over the past 740,000 years, especially the effects of carbon dioxide,
methane and other components of the atmosphere.
The results will be used to test and enhance computer models used to
predict future climate. EPICA's
aim is to drill two ice cores to the base of the Antarctic ice sheet, one at
Dome C, and the other in Dronning Maud Land.
Both drillings hope to reach their aim in the next 2 years.
The
ice cores are cylinders of ice 10 cm in diameter that are brought to the surface
in lengths of about 3 metres at a time. Snowflakes
collect particles from the atmosphere, and pockets of air become trapped between
snow crystals as ice is formed. Analysis of the chemical composition and
physical properties of the snow and the trapped air, including atmospheric gases
such as CO2 and methane, shows how the Earth's climate has changed
over time.
The
Antarctic fieldwork is challenging both scientifically and environmentally.
Dome C (75° 06'S, 123° 21'E) is one of the most hostile places on
the planet, and average annual temperatures are below –54 degrees Celsius.
Researchers travel by tractor over thousands of kilometres of featureless
snow where blizzards are common.
The
20 million Euros project ‘European Project for Ice Coring in Antarctica' (EPICA)
is funded by the EPICA Steering Committee, The European Union and European
Science Foundation.
For further information, please
contact information@bas.ac.uk
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